1. Field of the Invention
The present invention relates to a voice paging service. More particularly, the present invention relates to a method and apparatus for transmitting a groupcast to support a voice paging service in a Voice over Internet Protocol (VoIP) system.
2. Description of the Related Art
Recently, based on the increased popularity and development of the Internet, a conventional telephone has been merged with technology used to support the Internet. The merging of the conventional telephone with Internet technology has allowed for replacing general phones with Internet phones. Internet phones are classified into a PC-to-PC type and a PC-to-phone type. Hereinafter, a service provided by Internet phones will be referred to as a Voice over Internet Protocol (VoIP) service.
An exemplary scheme for a voice paging service in a VoIP system includes a multicast scheme and a unicast scheme based on Digital Signal Processing (DSP). A multicasting address is necessary for multicast communication, and an Internet Group Management Protocol (IGMP) may be used to configure a multicasting group to perform packet transmission. That is, a voice message is transmitted with a multicasting address, which is transmitted by a multicasting router to users belonging to a group. The DSP-based unicast scheme allocates a DSP channel to each group user and performs Time Division Multiplexing (TDM), thereby unicast-transmitting a voice message to each terminal.
The multicast scheme efficiently transmits data between several transmitters/receivers in an n to n communication environment. However, the multicast scheme has a limitation in that all the routers in the network must retain information dynamically in order to forward a multicasting packet and a VoIP Private Branch eXchange (PBX), a VoIP phone and all the routers in the network must support a multicast routing protocol. Also, the multicast scheme is unsuitable for a 1 to n small-scale communication environment such as voice paging of the VoIP PBX. Also, the multicast scheme may cause an overhead in the network due to multicasting. Also, it is difficult for the multicast scheme to provide a Network Address Translation (NAT) for a VoIP phone in an NAT environment and implement independent traffic management. The DSP-based unicast scheme may waste resources because it must allocate a DSP channel to a group user.
What is therefore required is a method and apparatus for transmitting a groupcast to support a voice paging service in a VoIP system.